A conventional string clamping device of a threading machine for a racket contains: a clamp unit, a tightening unit, a connection column, and an adjustment member.
The clamp unit includes a body and a fixing seat which are configured to clamp two first springs, wherein the tightening unit has an operation handle, and the tightening unit clamps two steel balls and a second spring so as to abut against the fixing seat of the clamp unit. The clamp unit includes two adjustment bolts configured to adjust the fixing seat to move forward and backward, the connection column connects the clamp unit and the tightening unit together, and the adjustment member rotates into the clamp unit so as to adjust tightness between the body of the clamp unit and the fixing seat.
Between the body and the fixing seat is defined a gap configured to accommodate strings. The adjustment member is rotated so as to drive the connection column to actuate a locking block of the tightening unit, and the locking block moves so as to adjust a width of the gap based on a diameter of the strings.
However, as threading the strings onto the racket, the strings are clamped by the body and the fixing seat, a resistance force of the strings is against the body and the fixing seat, the adjustment member and the connection column move, and the width of the gap expands, hence the adjustment member is rotated repeatedly so as to adjust the width of the gap troublesomely.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.